Tonawanda News

August 18, 2013

FIT FOR LIFE: Glycemic index: useful or useless?

The Tonawanda News

Tonawanda News — People who pay attention to conversations about diet these days may often be under the belief that complex carbohydrates break down in our bodies slower than simple carbs, providing more nourishment and keeping us feeling full longer.

So, people who want to eat healthy should eat complex carbs and everything is good, right? Not so fast.

To this day, many fitness enthusiasts, body-builders, figure competitors and fans of pseudo-science stake everything on a foods glycemic index score, but that data is not perfect, consistent or fail-proof.

If we dig (great Incubus song) a little bit deeper, we have several indexes to refer to, and we can start with the gylcemic index, which gives insight as to how carbs impact blood glucose (sugar) levels, but can also consider the insulin index and the satiety index.

Let’s look at the glycemic index first.

The following foods are complex carbs with low to moderate ratings on the glycemic index: kidney beans, 28, rye bread, 50, brown rice, 55, old-fashioned oatmeal, 58, and sweet corn, 60.

Complex carbs with higher ratings on the glycemic index include whole-wheat bread, 70, white bread, 73, Cheerios, 74, and white rice, 92.

However, with regards to the insulin index, protein-rich foods such as baked beans and refined carbs (pastries, etc.) caused insulin responses that were higher than their glycemic index might suggest. 

The satiety index of foods is also a ranking system, examining a food’s ability to satisfy hunger. The higher the ranking, the more satisfying the food.

The amount of fiber, protein and water within the food are typically the general agents of satiety. Some low-satiety food are: croissant 47, cake 65, ice cream 96, French fries, 116, Special K, 116.

Higher satiety food include: grain-bread 154, popcorn, 154, grapes 162, baked beans, 168, beef, 176, apples, 197, potatoes 323.

As you can see, there are some surprises as some foods score low on the glycemic index but have a higher satiety score.

What are limitations of the glycemic index?

GI values are determined using that particular food item only. What’s the big deal you say? Very rarely do you only eat one particular food and nothing else. Who only consumes a potato or only Special K and nothing else?

GI values are also determined from a fasted state, which is typically unlikely in real life. This means that any digestion/absorption of other foods are taken out of the equation. The acidity of food, amount of fat, fiber and certain proteins can lower GI response. Freezing white bread lowers its Glycemic Index rating.

There is also a weakness of the satiety index.

Greater satiety is typically associated with lower GI food items. However, all of this data comes from single-meal experiments. Some of the studies aren’t controlled for calorie intake either. Some subjects have eaten more than other subjects. There are huge study weaknesses there.

Other inconsistencies: Low GI milk has a high insulin index compared to high GI white bread. Low GI baked beans have a high insulin index of 120.

Foods that should have a low GI due to fat content (fat typically slows absorption) do not always have a low GI. Examples are; fries, cookies and doughnuts. The above foods also have a high insulin index. One theory is due to the saturated fat content.

So the main problem with using the above tools to determine a particular food’s “edibleness” level? Food discrimination.

Like most studies you can single out data to either validate or crush an argument. I can’t even begin to tell you how many clients/gym goers have abandoned white potatoes in favor of sweet potatoes. This is a pretty simplistic bias that “white” foods are bad/less nutritious and are responsible for the national debt versus darker and or more colorful food choices. 

Examples of nutritional bias: A sweet potato has more fiber, more Vitamin A, higher in most B vitamins, higher in calcium and higher in manganese than a russet potato. In contrast, a russet potato is higher in iron and magnesium, higher in phosphorus, higher in potassium, higher in protein and selenium. This proves it’s foolish to deem one food type superior over another. 

One food lacks in certain qualities that the other excels in. This is also assuming all vitamins/minerals/nutrients have been identified/discovered. 

Long-awaited conclusion

Glycemic Index, Insulin Index and the Satiety Index give us generalizations and clues of certain foods. There are too many variables to allow any of the above to accurately determine whether or not a food is “good” or “bad.” It’s best to keep things simple, eat a variety of food, train smart and hard and enjoy the journey.

Chris Tybor is a personal trainer and owner of Christfit, which has locations in Lewiston and Niagara Falls. For more information visit